The health regulator said that it would continue to investigate counterfeit Ozempic 1-milligram injections and had seized thousands of units, but that some might still be available for purchase.
Danish drugmaker Novo Nordisk and the FDA are testing the seized products and do not yet have information about the drugs' identity, quality or safety, the agency said.
Novo said the seizures took place in warehouses outside the company's authorized supply chain.
The agency said the needles from the seized injections were counterfeit and their sterility could not be confirmed, which presented an additional risk of infection for patients.
Other confirmed counterfeit components from the seized products included the pen label and accompanying information about the health care professional and patient as well as the carton.
The FDA urged drug distributors, retail pharmacies, health care practitioners and patients to check the drugs they have received and to not distribute, use or sell the units labeled with lot number NAR0074 and serial number 430834149057.
The regulator said it was aware of five adverse events resulting from use of the drug belonging to this lot, but all of them were consistent with known side-effects related to authentic Ozempic.
Demand for Wegovy and Ozempic is exceeding Novo's supply of the drugs in the United States, Germany and Britain, leading the company to restrict supplies of certain doses of Wegovy to the U.S. market.
Though only Wegovy is approved for obesity, its diabetes counterpart Ozempic also leads to dramatic weight loss, which has led people in the United States and Europe to use the drug off-label, meaning not for its approved use.